It is important to realise that there is massive irony in the Intended's comment that she knew Kurtz best. The way that the Intended has responded to the death of Kurtz by wearing mourning and letting it impact her for the rest of her life, and the way that she talks about him, indicates that she doesn't really know Kurtz at all, not in the way that Marlow knows him and has experienced the true depth of his depravity. In a sense, the Intended's feelings about Kurtz are paralleled by the feelings of the majority about colonialism. Both are lauded and praised and thought of as being wonderful, whereas the reality is something very different. As if to signal this naievety, Marlow records that "with every word spoken the room was growing darker," metaphorically indicating her ignorance and the darkness of her awareness of the true nature of Kurtz. In spite of her claims to have known Kurtz, actually, the text indicates, she didn't know him at all.